This invention relates to improvements in brakes, and more particularly to a reservoir for a master cylinder for the hydraulic brakes of a motor vehicle.
One type of master cylinder system and the type to which this invention relates is commonly referred to as a split system or tandem master cylinder system. A master cylinder in such a system has a reservoir above it to provide the additional fluid needed as the brake shoes wear, for example, and has distinct and separate connections to two sets of brakes, such as to the rear wheel brakes and the front wheel brakes or to two sets of brakes each set of which includes one front wheel brake and one diagonally located rear wheel brake. The reservoir is conventionally divided into two chambers, one for the primary piston chamber (for one set of brakes) and one for the secondary piston-chamber (for the other set of brakes). If one set of brakes malfunctions in such a way that a drop in hydraulic pressure occurs in such set, the other set will continue to operate.
Various types of reservoirs with different partitioning arrangements are shown in U.S. Pat. Nos. 3,147,596; 3,194,019; 3,520,136 and 3,731,487. The first three patents show partitions which extend up from the bottom of the reservoir and part way toward the cap or top thereof. These arrangements permit the reservoir to be filled through one inlet as the fluid will eventually flow over the partitions into the other sections of the reservoir. U.S. Pat. No. 3,731,487, shows a partition which, except for a pressure bleed-through passage, completely blocks communication between two sections of a reservoir. In such an arrangement the reservoir cover is completely removed when hydraulic fluid must be added.
One of the problems encountered with reservoirs having partial partitions occurs during braking deceleration periods. Under these conditions fluid tends to slosh over the partition due to the build-up of the fluid toward the front of the particular section of reservoir. For example, during a one G deceleration, the surface of fluid in a reservoir section will extend at a 45.degree. angle and fluid will tend to flow from the rearward section to the forward section. If the rear brake system should develop a leak, for example, the supply of fluid in the front reservoir section, from which fluid is supplied to such system, would gradually be depleted. During each braking operation, fluid from the rear reservoir section, would flow over the partition into the front section. Thus, not only would the rear brakes eventually be rendered ineffective due to the loss of fluid from the rear brake system, but the front brakes would eventually be rendered ineffective due to the depletion of fluid in the rear reservoir. Similar situations could be presented under acceleration conditions, during cornering manuevers and with vehicle vibration. Obviously, such situations are not desirable.
Some master cylinders, such as the type shown in U.S. Pat. No. 3,731,487, require a special seal located ahead of the secondary piston to inhibit pumping of fluid past such piston, into the rear reservoir section. This seal is shown at 79 in U.S. Pat. No. 3,731,487. It would be desirable if such a seal were unnecessary, thus permitting the pistons, and master cylinder to be shortened, resulting in a weight reduction.
The present invention overcomes some of the shortcomings of reservoirs of the type described above.